全 文 ：高含游离脂肪酸的香果树籽油制备生物柴油的方法*
颜摇 健, 邱摇 頔, 陆摇 璐, 周摇 琳, 李忠荣, 邱明华**
(中国科学院昆明植物研究所植物化学与西部植物资源持续利用国家重点实验室, 云南 昆明摇 650201)
摘要: 目前生物柴油因其环保和可再生利用资源的特性备受关注。 多数生物柴油是通过甲醇和碱催化食用
油得到的, 而大量非食用油也可以制备生物柴油。 本文报道用高含游离酸脂肪油快速高效低成本制备成其
单酯的二步法工艺。 先用 1% H2SO4 以少于 1. 5%量对甲醇和云南特产香果树 (Lindera communis) 籽的粗
原料油以 10 颐 1 摩尔比组成的混合液酸催化酯化游离脂肪酸; 之后再对醇和得到的油脂产品按摩尔比 15 颐 1
的混合液碱催化转化为单甲酯和甘油。 本方法是一个直接甲脂化制备生物柴油的工艺简洁、 降低成本的新
技术。 文中还讨论了该工艺影响转化效率的主要因素, 如摩尔比, 催化量, 温度, 反应时间和酸度。 香果
树生物柴油不重蒸, 而其生物柴油的主要特性, 如粘度、 热值、 比重、 闪点、 冷滤点等与生物柴油标准的
匹配度, 也做了报道, 研究结果将为香果树生物柴油以非重蒸油料制备生物柴油产品, 作为潜在的柴油燃
料替代产品提供技术支撑。
关键词: 香果树籽油; 生物柴油; 甲酯化
中图分类号: Q 946摇 摇 摇 摇 摇 摇 文献标识码: A摇 摇 摇 摇 摇 摇 摇 文章编号: 2095-0845(2013)01-089-06
Biodiesel Production from High FFA Oil of
Lindera communis (Lauraceae)
YAN Jian, QIU Di, LU Lu, ZHOU Lin, LI Zhong鄄Rong, QIU Ming鄄Hua**
(State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany,
Chinese Academy of Sciences, Kunming 650201, China)
Abstract: Currently, biodiesel has become more attractive because of its environmental benefits and the fact that it
is made from renewable resources. Most of the biodiesel are from the refined edible type of oil using methanol and al鄄
kaline catalyst. However, larger amount of non鄄edible oil are available. A two鄄step rapid and efficient low鄄cost
transesterification process was developed to convert the high FFA crude oils to its mono鄄esters. Firstly, acid cata鄄
lyzed esterification reduced the FFA content of the gross Lindera communis oils to less then 1. 5% with 10 颐 1 molar
ratio methanol to oil in the presence of 1% H2SO4 (wt) as acid catalyst. Secondly, alkaline catalyzed transesterifi鄄
cation converted the products of the first step to single ester (biodiesel) and glycerol with 15 颐 1 molar ratio methanol
and the product oil of first step. The major factors affected the conversion efficiency of the process were discussed,
such as molar ratio, amount of catalyst, temperature, reaction time and acid number. The biodiesel from Lindera
communis oil was not re鄄distillation, but its important properties such as viscosity, calorific value, specific gravity,
flash point, cloud point and pour point were matched with the standard demand. This study supported the biodiesel
product from unrefined L. communis oil as a potential replace to the diesel fuel.
Key words: Lindera communis oil; Biodiesel; Esterification
植 物 分 类 与 资 源 学 报摇 2013, 35 (1): 89 ~ 94
Plant Diversity and Resources摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 DOI: 10. 7677 / ynzwyj201312054
*
**
Foundation items: National Key Project of Scientific and Technical Supporting Programs (2007BAD32B00鄄1鄄3), Scientific Basic Research
Program (SB2007FY400) and NKIG of CAS (KSCX2鄄YW鄄G鄄027)
Author for correspondence; E鄄mail: mhchiu@ mail. kib. ac. cn
Received date: 2012-04-16, Accepted date: 2012-07-15
作者简介: 颜摇 健 (1978-) 男, 博士, 主要从事天然植物活性成分研究。
摇 One hundred years ago, Rudolf Diesel tested
vegetable oil as fuel for his engine (Shay, 1993).
In the 1930s and 1940s, vegetable oils were used as
diesel fuels from time to time, only in emergency situ鄄
ations. Recently, because of the increase in crude
oil price, limited resource of fossil oil and environ鄄
mental concerns, there has been a renewed focus on
vegetable oils and animal fats to make biodiesel fu鄄
el. Vegetable oils are becoming a promising alterna鄄
tive to diesel fuel because they have more advantages
than diesel fuel, such as renewable resources, local
production and friendly to environment. They have
practically no sulfur content and no storage difficul鄄
ty, furthermore, they have excellent lubrication
properties. In view of the several advantages, vege鄄
table oils have potential to replace petroleum鄄based
fuels in the long run.
In the recent years, systematic efforts had been
made by several researchers to use the various vege鄄
table oils as fuel in compression ignition engines.
The calorific value of vegetable oil is comparable to
that of diesel. However, their use in direct injection
diesel engines is restricted by some unfavorable
physical properties, particularly its viscosity. The
viscosity of vegetable oil is about ten times higher
than that of diesel. Therefore, the vegetable oil cau鄄
ses poor fuel atomization, incomplete combustion
and carbon deposition on the injection and valve
seats resulting in serious engine fouling ( Karmee
and Chadha, 2005). This necessitates reduction in
viscosity of the vegetable oils for use as fuel in en鄄
gines. The commonly employed methods to reduce
the viscosity of the oils are blending with diesel, e鄄
mulsification, pyrolysis, cracking and transesterifi鄄
cation ( Ramadhas et al., 2004 ). Among these,
transesterification of vegetable oils appears to be
more suitable. The transesterification reaction con鄄
sists of transforming triglycerides into fatty acid esters
by means of the action of an alcohol, with glycerin
remaining as byproduct (Encinar et al., 1999).
The difficulty with alkaline catalyzed esterifica鄄
tion of these oils is that they often contain larger a鄄
mounts of FFA. The FFA quickly reacts with alka鄄
line to product soaps that inhibit accomplishment of
the reaction and separation of the ester and glycerin.
However, Wide varieties of high free fatty acids
(FFA) oils are available in larger quantities. Lin鄄
dera communis oil is typical non鄄edible high FFA oil.
L. communi Hemsl. (Lauraceae), a perennial plant,
is widely distributed in Yunan, Gansu, Sichuan,
Guizhou, Hunan, Hubei, Guangdong, Guangxi, Fu鄄
jian, Shanxi, Taiwan and Zhongnan byland. Lindera
communi seed kernel (55% -60% of seed) contains
50% -55% (wt) of fawn鄄coloured oil. L. communi
tree yields 2鄄seeded ellipsoidal capsule, and varies
in size 0. 5 -0. 8 cm long, brown, weighing 37 mg
more or less. Seed is half鄄ellipsoid, weighing about
24 mg. L. communis oil is considered as a potential
feedstock for biodiesel product. The purpose of the
present study is to develop a method for esterification
of high FFA vegetable oils.
1摇 Results and discussion
The FFA content of L. communis oil is corre鄄
sponding acid value of 27. 5 mg KOH / g, which is
far above the 1% limit for satisfactory transesterifica鄄
tion reaction using alkaline catalyst (Ghadge et al.,
2005). Therefore, in order to reduce the acid value
(ie. for reducing FFA), the FFA oil was firstly con鄄
verted to esters in first鄄step treatment process using
acid catalyst, then the sample was continued to react
to get biodiesel with alkaline catalyst. So, the ratios
between oil and methanol, catalyst amount, duration
time were discussed in following part.
1. 1摇 Acid esterification ( first step)
1. 1. 1摇 Effect of methanol to oil molar ratio
First of all, the molar ratio of methanol to plant
oil is considered as an important factor that affects
the conversion efficiency as well as cost of biodiesel.
The conversion efficiency is defined as the yield of
the process represented in terms of percentage. Mo鄄
lar ratio is the ratio of number of between molar of
methanol and molars of glycerides in the oil (oil av鄄
erage molecular weight about 820). Transesterifica鄄
09摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 植 物 分 类 与 资 源 学 报摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 第 35 卷
tion reaction requires three molars of alcohol for each
molar of oil. However, in practice, the molar ratio
should be higher than that of theoretics in order to
drive the reaction towards completion. Canakci and
Van advocated the use of large excess quantities of
methanol (15 颐 1-35 颐 1) while using the sulphuric
acid as catalyst ( Canakci and Van, 1999 ). The
conversion efficiency of the first step in relation with
molar ratio was obtained ( Fig. 1). The maximum
conversion efficiency was achieved very close to the
molar ratio of 10 颐 1. Further increase in molar ratio
there was only a little improvement in the conversion
efficiency. So we suggest that trial would be carried
with molar ratio 10 颐 1.
Fig. 1摇 Effect of molar ratio on conversion efficiency (step 1)
1. 1. 2摇 Effect of acid catalyst amount
The amount of acid catalyst used in the process
of the first step also affects the conversion efficiency.
The catalyst amount was varied in the range from
0. 3% -2. 5% for six different values (0. 3, 0. 5, 1,
1. 5, 2, 2. 5% of sulphuric acid). The effect of cat鄄
alyst amount on the conversion efficiency was shown
in Fig. 2. The acid鄄catalyst process attained the max鄄
imum conversion efficiency at 1% of sulphuric acid.
Fig. 2摇 Effect of acid catalyst amount on the
conversion efficiency (step 1)
Besides, it was noted that excessive addition of sul鄄
phuric acid darkened the color of the product, while
lower amount of sulphuric acid addition affected the
yield of the next step.
1. 1. 3摇 Effect of reaction temperature and duration
At room temperature, the ester reaction was
noted to be extraordinary low even after a day, even
stirring. With increase in temperature, the reaction
took place at a faster rate. The optimum temperature
for the reaction was found in the range of 55 益 依5 益.
At higher temperature, there was a chance of in鄄
crease in darkness of the product and increase the
product total cost of biodiesel.
Reaction time was also a factor that affected the
yield of the first step, even next step. We sampled
the mixture during reacting at 0. 5 h, 1 h, 1. 5 h,
2 h, 3 h, 4 h, 8 h, then measured the conversion ef鄄
ficiency. We found that the reaction was almost ac鄄
complished in 1 h.
1. 2摇 Alkaline esterification (second step)
1. 2. 1摇 Effect of methanol to oil molar ratio
The amount of methanol required for esterifica鄄
tion was analyzed in terms of the molar ratio. Theo鄄
retically, the methanol / triglyceride molar ratio re鄄
quired is 3 颐 1. But, in practice this is not sufficient
to complete the reaction. Higher molar ratio is re鄄
quired to drive the reaction to completion at a faster
rate and good conversion efficiency. We observed
that lower molar ratio required longer period, even
the reaction did not arise. The effect of molar ratio
on conversion efficiency was shown in Fig. 3. It
showed that yield of the process became higher with
increase methanol volume, arrived the maximum es鄄
ter yield at the molar ratio of 10 颐 1. The conversion
efficiency had little change with further increase
methanol volume, but the lucidity continued clearer
optically. Based on the two sides above, molar ratio
of 15 颐 1 was optimal. The excess methanol was re鄄
moved from the product. Then the mixture was poured
into flask. After a while, the glycerin and little impuri鄄
ty were discharged at low layer. The upper layer was
washed 3-4 times by hot water (55 益), then was
191 期摇 摇 摇 摇 摇 YAN Jian et al. : Biodiesel Production from High FFA Oil of Lindera communis (Lauraceae) 摇 摇 摇 摇 摇
dried. At last, the yellowy liquid was biodiesel.
Fig. 3摇 Effect of molar ratio on conversion efficiency
1. 2. 2摇 Effect of alkaline catalyst amount
The alkaline catalyst potassium hydroxide con鄄
centration was used in the experiment from range of
0. 3% -2. 5% (weight of KOH / wight of oil) . The
maximum conversion efficiency was arrived at 1% of
KOH. Addition excess catalyst gave rise to the for鄄
mation of an emulsion, which increased the viscosity
and led to the formation of gels, while the reaction
did not take place if the amount of KOH was not e鄄
nough. The effect of catalyst amount of conversion
effect was shown in Fig. 4.
Fig. 4摇 Effect of alkaline catalyst amount on conversion efficiency
1. 2. 3摇 Effect of reaction temperature
Other research achieved best results at 45 益 and
up to 70 益 while using rubber seed oil and brassica
carinata oil (Ramadhas et al., 2005; Pilar et al.,
2004), respectively. However, the maximum yield
of boidesel from L. communi oil was obtained at the
temperature of (55 依 5) 益 . The decrease in yield
was observed when the reaction temperature went
above 60 益 .
1. 2. 4摇 Effect of reaction duration
It had been observed that the ester yield slightly
increase in reaction duration. Results obtained from
the present experiments revealed that the reaction
was completed for 30 minutes. We noticed that lu鄄
cidity of the mixture suddenly changed when the re鄄
action was finished. If we prolonged time, the yield
was not increase.
1. 3摇 Investigation of method of washing with hot
distilled water
This method was applied by washing the mix鄄
ture with distilled water at three different tempera鄄
tures (25, 50, 80 益) in two鄄step process. When the
reaction was finished, the methyl ester and glycerin
were separated in funnel. The crude ester phase was
washed with hot distilled water 3 颐 2 (oil 颐 water, v)
in the following order: former two times without stir鄄
ring and the third time with gently stirring. We ob鄄
served that separation was difficulty using room tem鄄
perature water (25 益) because oil and cold water
did not dissolve. However, using hot water (80 益),
separation time was further longer and the yield was
lower than 50 益. So the best temperature was 50 益.
Hot water (依 50 益) was sprayed over the surface of
the ester two times and stirred gently in third time.
Lower layer was discarded and at last yellow color
layer (biodiesel) was separated.
1. 4摇 Characterization of L. communis oil
The oil was used as feedstock for biodiesel
product in this study, so the fatty acid composition
of the oil and biodiesel from L. communi were tested
by GC鄄MS. The results were shown in the Table 1.
The oil mainly was made up of C10, C12, C16 and
C18, which was match the biodiesel standard.
1.5摇 Properties of methyl esters of L. communis oil
The fuel properties of L. communis oil methyl
ester in comparison with that of other esters (Ghadge
et al., 2005) was shown in Table 2, respectively.
We concluded that the fuel properties were quite
comparable to those of other esters and diesel. The
present results showed that the transesterification
process improved the fuel properties of the oil with re鄄
spect to specific gravity, viscosity, flash point, and
acid value. The viscosity of the biodiesel was closer
29摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 植 物 分 类 与 资 源 学 报摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 第 35 卷
to that of diesel. Therefore, the existing engine was
not modified. The calorific values of biodiesel were
lower than diesel because of the oxygen content.
Biodiesel containing higher oxygen helped to com鄄
plete combustion of the oil in the engine. The flash
point was much higher than that of diesel. The flash
point was increased if the biodiesel and diesel were
mixed at percentage. Hence, it was safe to store and
transport the blends of biodiesel鄄diesel as compared
to diesel alone. The tested result showed that methyl
esters of the oil matched with DIN V 51606 biodiesel
standards (see Table 2).
Table 1摇 Composition of the oil and biodiesel from L. communi
Systemic name Struc鄄ture
Content / %
Material
oil
Biodi鄄
esel
Octanoic acid methyl ester C8 颐 0 0. 43
Decanoic acid methyl ester C10 颐 0 18. 66 31. 21
Undecanoic acid methyl ester C11 颐 0 0. 19
Dodecanoic acid methyl ester C12 颐 0 31. 51 41. 74
Tetradecanoic acid methyl ester C14 颐 0 1. 04 1. 77
Hexadecanoic acid methyl ester C16 颐 0 12. 93 11. 19
Octadecanoic acid methyl ester C18 颐 0 0. 65 0. 63
Cis鄄9鄄octadecenoic acid methyl ester C18 颐 1 18. 19 12. 70
Linoleic acid methyl ester C18 颐 2 5. 37
Eicosanoic acid methyl ester C20 颐 0 0. 14
2摇 Experimental
2. 1摇 Esterification Procedure
Experiments were conducted in a laboratory
scale setup of which 500 mL glass flask with con鄄
denser that retained any vaporized methanol to the
reacting mixture. A hot plate with magnetic stirrer
arrangement was used for heating the mixture in the
flask. The mixture was stirred at the same speed for
all tests. The temperature range of 50 益-60 益 was
maintained during experiment. One trial was carried
out for each reactant and process condition. The re鄄
sults were presented in Fig. s. Once the reaction was
finished no matter acid and alkaline catalyst, the
mixture immediately changed limpidity.
2.2摇 Analysis for material oil and biodiesel product
Firstly, Kernels were separated by breaking the
capsules with machine, dried to remove the mois鄄
ture. The kernels were crushed in the crusher and
the oil was filtered. The crude oil was reacted with
boron trifluoride鄄methanol complex for GC鄄MS (HP
GC6890 / MS5972) analysis. The biodiesel was ob鄄
tained by two step methods described in the paper
for GC鄄MS and properties of biodiesel. The machine
equipped with a HP鄄25 capillary column (30 m 伊
0. 25 mm i. d., 0. 25 滋m film thickness) and a mass
Table 2摇 Properties of biodiesel from L. communi oil
摇 摇 摇 摇 摇 摇 摇 Property Biodesel from L. communis oil German (DIN V 51606) Mahua biodiesel
Specific gravity (15 益) g / cm3 0. 875 0. 875-0. 90 0. 88
Calorific values MJ / Kg 37. 9摇 37. 0摇
Flash point 益 123 110 208
Pour point 益 -15 6
CFPP 益 -11 0-10 / -20
Viscosity at 20 益 mm2 / s 3. 22
Viscosity at 40 益 mm2 / s 5. 0摇 3. 5-5. 0 3. 98
Sulfated ash Wt% No detection 0. 03 max
Ash content Wt% 0. 01
Carbon residue Wt% 0. 02
Acid Value mgKOH / g 0. 034 0. 05 0. 20
Chroma 3. 5摇
Water content mg / kg No detection 300 max 0. 04
Erode for CU 1 1
Distillation 益
50% 293. 0
60% 309. 0
80% 332. 0
95% 338. 0
391 期摇 摇 摇 摇 摇 YAN Jian et al. : Biodiesel Production from High FFA Oil of Lindera communis (Lauraceae) 摇 摇 摇 摇 摇
spectrometer 5792. The carrier gas was helium, at a
flow rate of 1 mL / min. Column temperature was ini鄄
tially 50 益 for 1 min, then gradually increased to
180 益 at 5 益 / min, and finally increased to 260 益
at 15 益 / min. For GC鄄MS detection, an electron i鄄
onization system was used with an ionization energy
of 70 eV. The extracts were diluted 1 颐 100 ( v / v)
with diethyl ether, and 1. 0 滋L of the diluted sam鄄
ples was injected automatically in splitless mode. In鄄
jector and detector temperatures were set at 250 and
280 益, respectively.
3摇 Conclusion
The product of boidiesel from low鄄cost, high
FFA feedstock was investigated in the present study.
We found that the material with high FFA could not
be transesterified with the alkaline catalyst. The rea鄄
son was the catalyst (KOH or NaOH) to react with
the fatty acid to form soap that prevented the reaction
and separation from glycerin and ester. A two鄄step
was useful for the oil with high FFA. The first step
(acid catalyst) reduced the content of FFA ( less
than 1. 5% ) and converted the fatty acid to methyl
ester. The second step (alkaline catalyst) converted
the first product to mono鄄ester and glycerin. The
effects of methanol to oil molar ratio, catalyst a鄄
mount, reaction temperature, reaction time and wa鄄
ter washing method were analyzed in each step. No
matter acid catalyst or alkaline catalyst, the ratio of
methanol to oil was of importance in all conditions.
The molar ratio of methanol to oil 10 颐 1 completed
the process of reaction with 0. 5-1 hour. We noticed
that the react mixture suddenly changed lucidity,
suggesting the reaction was downright finished. The
abundance sulphuric acid darkened the product and
reduced the conversion efficiency. The excess alka鄄
line reduced the yield for adding wash times. The
maximum ester was achieved at the reaction temper鄄
ature in (55 依 5) 益 . The viscosity and acid value
was nearer to that of diesel. Point flash (about 127益)
was greater than that of diesel. Calorific value was
slightly lower than that of diesel. In a word, the
two鄄step method was useful for the non鄄edible oil
with FFA. According to our estimate, one tree of
10鄄year鄄old Lindera communis can produce 3 kilo鄄
grams of dried fruit for one year. The present study
revealed that biodiesel from unrefined the L. commu鄄
nis oil was quite suitable as an alternative to diesel.
Acknoledgements: The author was also grateful to the Yun鄄
nan Bureau of Quality and Technical Supervision for measur鄄
ing the property of oil. Ms. QIU Di, one of authors, now is a
university student of Beijing University of Posts and Telecom鄄
munications in CHINA.
References:
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49摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 植 物 分 类 与 资 源 学 报摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 第 35 卷